Estream is a portable water-power generator that converts any type of moving water, such as that from a river or stream, into stored energy to charge most of today's usb-connected mobile devices, even while you are off the grid. As a generator, it produces 2.5W - 5W of energy. As Estream is suspended in water, water flow rotates the turbine. The rotation enables the generator to generate electricity. Estream works well even in a weak current or behind your kayak. It takes about 4.5 hours to fully charge 6,400mAh built-in battery by running water. Once fully charges, the battery can charge up to 3 smartphones, GoPros or even tablet PCs, twice as fast as a regular outlet. It is rechargeable, so as long as you you have access to running water, you can continue to charge your devices - even on the longest adventures. Estream is easy to understand and use. It's light weight and is designed to fit in any size backpack.